Suzanne Finnamore seems to have lost her way as a writer. A decade ago, she won deserved praise for the polished wit and taut plotting of her first novel, a romantic comedy about the impending wedding of a materialistic and self-absorbed 36-year-old bride in a part of northern California where the Chilean Merlot runs deep.

Can credit cards ease a divorce?

Otherwise Engaged made clear that Finnamore knew what was wrong with writing “as rich as Croesus,” “at this point in time,” “in the very final analysis,” and the many similar phrases that turn up in her latest book. Her new memoir of her divorcehas the high-flying brand names and neuroses of her first novel, but the prose has turned cute and baggy.

Split suggests that Finnamore has begun to strip-mine her life for publication. At the age of 40, she may have gained new material when her husband walked out of their upscale northern-California home and began taking luxury vacations with a woman who soon became pregnant: The separation left her with a toddler, a mortgage, and “a meteor of repressed anger.”

But Finnamore skims over her pain in chapters so glib and short, she might have texted them to her publisher. In one scene, she goes a credit-card buying spree just when her income seems least certain. At warp speed, she spends $4,000 on more than a dozen frivolous items such as a “blond cardigan sweater with a detachable white mink collar” and a set of “blown-glass 14th-century French shoe reproduction Christmas ornaments.” She explains the binge by saying blithely that her purchases “have gotten me through this travesty” of a divorce. More alarmingly, she says that while smoking she set fire to “not one, not two, but five chenille throws”: “One mattress pad went down while I was on the phone to New York, as did two pillows and a luxury comforter.” Yes, divorce makes you crazy. But some of Finnamore’s behavior seems so reckless, you don’t know whether it results from the separation or from personality traits that were there all along.

Split is clearly not a how-to book, but what is it? Perhaps a coda to the “relationship autopsy” that a marriage counselor required Finnamore and her soon-to-be-ex husband to perform. The tone of Split resembles that of a breezy game of miniature golf the couple and their son played before the decree came through. “Even the pending divorce we just lightly reminisce over,” Finnamore writes, “as though it was a vacation to Fiji, where it rained.”

Best line: Finnamore’s son says while she is reading him a Christmas poem, “We’d better take Daddy’s stocking down, because he’s not going to be here tomorrow.” A rare poignant moment in a book long on wisecracks.

Worst line: Two categories here. Category No. 1: All of the clichés like those in the second paragraph of the review above. (“… it might, in the very final analysis, be some kind of elaborate prank.”) Category No. 2: All of the lines that make you wonder if Finnamore is exaggerating for comic effect or has a habit of self-destructive behavior that seems especially risky for someone who lives with a young child, such as her comment that she set fire to five chenille throws, apparently while smoking in bed.